Field of the Invention
The present invention relates to an organic electroluminescent display device, and more particularly, an organic electroluminescent display device and a method of driving the same.
Discussion of the Related Art
Commercially available display devices include cathode-ray tubes (CRT) and various types of flat panel displays. However, the various types of flat panel displays, such as liquid crystal display (LCD) devices, plasma display panel (PDP) devices, field emission display (FED) devices, and electroluminescent display (ELD) devices, are currently being developed as substitutes for the CRT. For example, advantages of LCD devices include a thin profile and low power consumption. However, LCD devices require a backlight unit because they are non-luminescent display devices. Organic electroluminescent display (OELD) devices, however, are self-luminescent display devices. OELD devices operate at low voltages and have a thin profile. Further, the OELD devices have fast response time, high brightness, and wide viewing angles.
FIG. 1 is a circuit diagram illustrating an OELD device according to the related art, and FIG. 2 is a timing chart of signals for operating the OELD of FIG. 1.
Referring to FIG. 1, the OELD device includes gate and data lines S and D crossing each other to define a sub-pixel region. The sub-pixel region includes a switching transistor SW, a capacitor C, a driving transistor DR and an organic emitting diode OLED.
Gate and source electrodes of the switching transistor SW are connected to the gate and data lines S and D, respectively. One electrode of the capacitor C is connected to a drain electrode of the switching transistor SW, and the other electrode of the capacitor C is connected to a reference voltage (VSS) source. Drain, gate and source electrodes of the driving transistor DR are connected to a cathode of the organic emitting diode OLED, the drain electrode of the switching transistor SW, and the reference voltage (VSS) source. An anode of the organic emitting diode OELD is connected to a power voltage (VDD) source.
Referring to FIG. 2, an nth gate voltage having a level of VGH is applied to a nth gate line S(n), a switching transistor SW connected to the nth gate line S(n) is turned on, and a data voltage Vdata is applied to the data line D and stored in the capacitor C. A current flowing in the driving transistor DR is determined according to a difference between the stored voltage in the capacitor C and the power voltage VDD. The OLED emits light according to the current passing through the OLED.